Solid electrolytic capacitor and production method therefor

ABSTRACT

A solid electrolytic capacitor includes: an insulating substrate; a capacitor element; a positive electrode lead-out structure; and a negative electrode lead-out structure. The positive electrode lead-out structure includes: a positive electrode terminal formed on the insulating substrate; a first positive electrode connection member formed on the insulating substrate; a second positive electrode connection member electrically connecting the first positive electrode connection member to the positive electrode terminal; and a pillow member configured to electrically connect the capacitor element to the first positive electrode connection member. The first positive electrode connection member has a recessed portion or a through hole. The recessed portion or the through hole overlaps an edge of a bottom surface of the pillow member having a first end of the recessed portion or the through hole disposed outside the edge and a second end of the recessed portion or the through hole disposed inside the edge.

RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/663,293, filed on Mar. 19, 2015, which is a Continuation ofInternational Patent Application No. PCT/JP2013/005717, filed on Sep.26, 2013, which in turn claims the benefit of Japanese Application No.2012-217238, filed on Sep. 28, 2012, the entire disclosures of whichApplications are incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to a solid electrolytic capacitorcomprising a capacitor element disposed on an insulating substrate, andmore particularly to a solid electrolytic capacitor characterized by anelectrode structure formed on an insulating substrate.

BACKGROUND

FIG. 21 is a cross-sectional view illustrating one example of aconventional solid electrolytic capacitor (refer to Unexamined JapanesePatent Publication No. 2010-123728, for example). As illustrated in FIG.21, the solid electrolytic capacitor comprises capacitor element 101 andinsulating substrate 102, and capacitor element 101 is disposed on anupper surface of insulating substrate 102. Capacitor element 101 haspositive electrode lead 103 and positive electrode body 113 serving as apositive electrode member, electrolytic layer 114 and negative electrodelayer 104 serving as a negative electrode member, and dielectric member115 interposed between the positive electrode member and the negativeelectrode member. On the upper surface of insulating substrate 102,positive electrode connection member 105 and negative electrodeconnection member 106 are disposed separately from each other. On alower surface of insulating substrate 102, positive electrode terminal107 and negative electrode terminal 108 are disposed separately fromeach other. Furthermore, insulating substrate 102 has positive electrodeconductive via 109 and negative electrode conductive via 110 each formedby making a hole penetrating from the upper surface to the lower surfaceand filling the hole with a conductive material. Positive electrodeconductive via 109 electrically connects positive electrode connectionmember 105 to positive electrode terminal 107, and negative electrodeconductive via 110 electrically connects negative electrode connectionmember 106 to negative electrode terminal 108. In addition, positiveelectrode connection member 105 and positive electrode lead 103 areelectrically connected to each other with pillow member 111 interposedtherebetween. Furthermore, negative electrode connection member 106 andnegative electrode layer 104 are electrically connected to each otherwith conductive paste 112 interposed therebetween.

Pillow member 111 shown in FIG. 21 is disposed on a main surface ofpositive electrode connection member 105 before capacitor element 101 isdisposed on the upper surface of insulating substrate 102. At this time,pillow member 111 is bonded to positive electrode connection member 105with conductive bonding member 116.

SUMMARY

A solid electrolytic capacitor according to the present disclosurecomprises an insulating substrate having an upper surface and a lowersurface, a capacitor element disposed on the upper surface of theinsulating substrate, a positive electrode lead-out structure, and anegative electrode lead-out structure. The capacitor element has apositive electrode member, a negative electrode member, and a dielectricmember. The positive electrode lead-out structure has a positiveelectrode terminal formed on the lower surface of the insulatingsubstrate and is electrically connected to the positive electrode memberof the capacitor element. The negative electrode lead-out structure hasa negative electrode terminal formed on the lower surface of theinsulating substrate and is electrically connected to the negativeelectrode member of the capacitor element. The positive electrodelead-out structure further comprises a first positive electrodeconnection member, a second positive electrode connection member, apillow member, and a positive electrode bonding member. The firstpositive electrode connection member has a main surface and a backsurface, and the back surface is in contact with the upper surface ofthe insulating substrate. Thus, the first positive electrode connectionmember has a recessed portion formed by locally recessing the mainsurface, or a through hole penetrating from the main surface to the backsurface. The second positive electrode connection member electricallyconnects the first positive electrode connection member to the positiveelectrode terminal. The pillow member has a top surface and a bottomsurface, and electrically connects the positive electrode member of thecapacitor element to the first positive electrode connection member. Thepositive electrode bonding member bonds the pillow member to the firstpositive electrode connection member. Thus, the positive electrodebonding member partially enters the recessed portion or the through holein the first positive electrode connection member, and is in contactwith an edge of the bottom surface of the pillow member at a positionabove the recessed portion or the through hole, or at the nearbyposition.

According to the solid electrolytic capacitor, the recessed portion orthe through hole is provided at a position where the pillow member is tobe disposed. The positive electrode bonding member partially enters therecessed portion or the through hole, and the edge of the bottom surfaceof the pillow member is disposed at the position above the recessedportion or the through hole, or at the nearby position. In this way, theposition of the pillow member is prevented from being largely displacedfrom the position where the pillow member is to be disposed. Therefore,according to the solid electrolytic capacitor, the positive electrodemember of the capacitor element and the pillow member can be surelyconnected to each other, so that the electrical connection defect ishardly generated between these members.

According to a preferable specific configuration of the solidelectrolytic capacitor, the bottom surface of the pillow member has apolygonal shape having plural corners and plural sides, and the recessedportion or the through hole is formed in the first positive electrodeconnection member at a position that overlaps with the corner withrespect to at least two corners among the plural corners. Alternatively,or in addition to this, the recessed portion or the through hole isformed in the first positive electrode connection member at a positionthat overlaps with the side with respect to at least two sides among theplural sides.

According to another preferable specific configuration of the solidelectrolytic capacitor, the second positive electrode connection memberis a conductive via penetrating the insulating substrate from the uppersurface to the lower surface, and the recessed portion or the throughhole in the first positive electrode connection member is disposed abovethe conductive via.

A manufacturing method according to the present disclosure is a methodfor manufacturing a solid electrolytic capacitor comprising aninsulating substrate having an upper surface and a lower surface, acapacitor element disposed on the upper surface of the insulatingsubstrate, a positive electrode lead-out structure, and a negativeelectrode lead-out structure. Here, the capacitor element has a positiveelectrode member, a negative electrode member, and a dielectric member.The positive electrode lead-out structure has a positive electrodeterminal formed on the lower surface of the insulating substrate and iselectrically connected to the positive electrode member of the capacitorelement. The negative electrode lead-out structure has a negativeelectrode terminal formed on the lower surface of the insulatingsubstrate and is electrically connected to the negative electrode memberof the capacitor element. According to the manufacturing method, a firstpositive electrode connection member is formed on the upper surface ofthe insulating substrate, and a recessed portion formed by locallyrecessing a main surface of the first positive electrode connectionmember or a through hole penetrating the first positive electrodeconnection member from the main surface to a back surface. Subsequently,a bonding agent containing a conductive material is applied to the mainsurface of the first positive electrode connection member. After that, apillow member is disposed on the first positive electrode connectionmember. At this time, a bottom surface of the pillow member comes incontact with the bonding agent, and an edge of the bottom surface of thepillow member overlaps with the recessed portion or the through hole inthe first positive electrode connection member. After that, theconductive material is melted by heating the bonding agent.

According to the manufacturing method, a predetermined position in whichthe pillow member is to be disposed is defined by positions of therecessed portions or the through holes. However, when the pillow memberis disposed on the first positive electrode connection member, thepillow member could be displaced from the predetermined position.According to the manufacturing method, when the conductive material ismelted by heating the bonding agent, the melted conductive materialflows into an inside of the recessed portion or the through hole, sothat the melted conductive material flows in the bonding agent. Thus,due to this flow, the pillow member receives forces in variousdirections along the main surface of first positive electrode connectionmember. When the position of the pillow member roughly coincides withthe predetermined position, the forces applied to the pillow membercancel each other out, and as a result, the pillow member is maintainedin the predetermined position. Meanwhile, when the position of thepillow member is displaced from the predetermined position, the forceapplied in a direction displaced from the predetermined position issmaller than the force applied in its opposite direction. As a result,the pillow member is drawn to the predetermined position, and theposition of the pillow member roughly coincides with the predeterminedposition. Thus, the positive electrode member of the capacitor elementis surely in contact with the pillow member and as a result, anelectrical connection defect is hardly generated between them in themanufactured solid electrolytic capacitor.

According to a preferable specific configuration of the manufacturingmethod, the conductive material contained in the bonding agent haswettability in a melted state with respect to the first positiveelectrode connection member. Thus, when the conductive material ismelted by heating the bonding agent, the melted conductive material getswet and spreads along the main surface of the first positive electrodeconnection member, and is likely to flow into the inside of the recessedportion or the through hole formed in the first positive electrodeconnection member. As a result, the melted conductive material is likelyto flow in the bonding agent.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view illustrating a solid electrolyticcapacitor according to a first exemplary embodiment of the presentdisclosure.

FIG. 2 is a top view of a region II illustrated in FIG. 1.

FIG. 3 is a cross-sectional view to be used for describing a firstprocess in an electrode forming step to be executed by a method formanufacturing the solid electrolytic capacitor according to the firstexemplary embodiment.

FIG. 4A is a cross-sectional view to be used for describing a secondprocess in the electrode forming step.

FIG. 4B is a top view to be used for describing a second process in theelectrode forming step.

FIG. 5 is a cross-sectional view to be used for describing a thirdprocess in the electrode forming step.

FIG. 6A is a cross-sectional view to be used for describing a fourthprocess in the electrode forming step.

FIG. 6B is a top view to be used for describing a fourth process in theelectrode forming step.

FIG. 7A is a cross-sectional view to be used for describing a fifthprocess in the electrode forming step.

FIG. 7B is a top view to be used for describing a fifth process in theelectrode forming step.

FIG. 8 is a top view illustrating a state in which a pillow member isdisplaced from a predetermined position in the fifth process.

FIG. 9A is a cross-sectional view to be used for describing a sixthprocess in the electrode forming step.

FIG. 9B is a top view to be used for describing a sixth process in theelectrode forming step.

FIG. 10 is a top view illustrating a state in which the pillow member isdrawn to the predetermined position in the sixth process.

FIG. 11 is a cross-sectional view illustrating a solid electrolyticcapacitor according to a second exemplary embodiment of the presentdisclosure.

FIG. 12 is a cross-sectional view illustrating another example of apositive electrode lead-out structure in the solid electrolyticcapacitor according to the second exemplary embodiment.

FIG. 13 is a cross-sectional view to be used for describing a firstprocess in an electrode forming step to be executed by a method formanufacturing the solid electrolytic capacitor according to the secondexemplary embodiment.

FIG. 14 is a cross-sectional view to be used for describing a secondprocess in the electrode forming step.

FIG. 15 is a cross-sectional view to be used for describing a thirdprocess in the electrode forming step.

FIG. 16 is a cross-sectional view to be used for describing a fourthprocess in the electrode forming step.

FIG. 17 is a cross-sectional view to be used for describing a fifthprocess in the electrode forming step.

FIG. 18A is a cross-sectional view to be used for describing a sixthprocess of the electrode forming step.

FIG. 18B is a top view to be used for describing a sixth process of theelectrode forming step.

FIG. 19 is a cross-sectional view illustrating a variation of thepositive electrode lead-out structure.

FIG. 20 is a cross-sectional view illustrating another variation of thepositive electrode lead-out structure.

FIG. 21 is a cross-sectional view illustrating an example of aconventional solid electrolytic capacitor.

DESCRIPTION OF EMBODIMENT

Problems which exemplary embodiments of this disclosure intend to solveare as follows.

According to a conventional technique, when pillow member 111 isconnected to positive electrode connection member 105 with conductivebonding member 116, a position of pillow member 111 is likely to bedisplaced from a predetermined position in which pillow member 111 is tobe disposed. Here, this predetermined position means a position at whichpositive electrode lead 103 surely comes in contact with pillow member111 when capacitor element 101 is disposed on insulating substrate 102.Recently, as the solid electrolytic capacitor is miniaturized, pillowmember 111 becomes small in size, and the above displacement noticeablyoccurs. Therefore, after capacitor element 101 has been disposed on theupper surface of insulating substrate 102, an electrical connectiondefect is likely to be generated between positive electrode lead 103 andpillow member 111.

Thus, the present disclosure provides a solid electrolytic capacitorthat hardly generates an electrical connection defect between a positiveelectrode member of a capacitor element and a pillow member, and amethod for manufacturing the same.

FIG. 1 is a cross-sectional view illustrating a solid electrolyticcapacitor according to a first exemplary embodiment of the presentdisclosure. As illustrated in FIG. 1, the solid electrolytic capacitorcomprises capacitor element 1, insulating substrate 2, positiveelectrode lead-out structure 3, negative electrode lead-out structure 4,and exterior body 5.

Capacitor element 1 has positive electrode body 11, positive electrodelead 12, dielectric layer 13, electrolytic layer 14, and negativeelectrode layer 15. Positive electrode body 11 is configured to be aconductive porous sintered body. Positive electrode lead 12 isconfigured to be a conductive wire. Positive electrode lead 12 isembedded into positive electrode body 11, and a part (lead-out portion12 a) of positive electrode lead 12 is drawn out of an outer peripheralsurface of positive electrode body 11.

As a conductive material for positive electrode body 11 and positiveelectrode lead 12, the same kind or different kinds of materials areused. The conductive material includes a valve metal such as titanium(Ti), tantalum (Ta), aluminum (Al), or niobium (Nb). Especially,titanium (Ti), tantalum (Ta), aluminum (Al), or niobium (Nb) is asuitable material to be used because its oxide (dielectric layer 13) hasa high dielectric constant. Furthermore, the conductive material may bean alloy including at least two kinds of valve metals, an alloyincluding the valve metal and another material, or an alloy containingthe valve metal as its major component.

Dielectric layer 13 is formed on a surface of positive electrode body 11composed of the conductive material. More specifically, dielectric layer13 is an oxide film formed by oxidizing the surface of the positiveelectrode body 11 composed of the conductive material. Therefore,dielectric layer 13 is formed on an outermost peripheral surface ofpositive electrode body 11, and on inner peripheral surfaces of fineholes formed in positive electrode body 11. In FIG. 1, dielectric layer13 is schematically illustrated to be formed only on the outermostperipheral surface of positive electrode body 11.

Electrolytic layer 14 is formed on a surface of dielectric layer 13.More specifically, electrolytic layer 14 is formed on an outermostperipheral surface of dielectric layer 13, and over inner surfaces ofthe fine holes in positive electrode body 11. The examples ofelectrolytic layer 14 are an electrolytic material including aconductive inorganic material such as manganese dioxide, and aconductive organic material such as tetracyano-quinodimethane (TCNQ)complex salt or conductive polymer. Furthermore, the electrolyticmaterial is not limited to the conductive inorganic material and theconductive organic material, and includes various kinds of materials.

Negative electrode layer 15 is formed on an outermost peripheral surfaceof electrolytic layer 14. More specifically, negative electrode layer 15comprises a carbon layer (not shown) formed on the outermost peripheralsurface of electrolytic layer 14, and a silver paint layer (not shown)formed on an outer peripheral surface of the carbon layer. In addition,negative electrode layer 15 is not limited to this, and any kind ofmaterial may be used as long as negative electrode layer 15 has anelectricity collecting function.

As described above, positive electrode body 11 and positive electrodelead 12 serve as a positive electrode member of capacitor element 1,electrolytic layer 14 and negative electrode layer 15 serve as anegative electrode member of capacitor element 1, and dielectric layer13 serves as a dielectric member of capacitor element 1. Furthermore,the positive electrode member may be a metal foil sheet or metal platecomposed of the above valve metal.

Insulating substrate 2 is a flat substrate composed of an electricalinsulating material such as polyimide or glass epoxy, and has uppersurface 2 a and lower surface 2 b. Capacitor element 1 is disposed onupper surface 2 a in such a manner that an extending direction ofpositive electrode lead 12 becomes parallel to upper surface 2 a.

Positive electrode lead-out structure 3 is an electrode structure thatleads a positive electrode current path connecting positive electrodelead 12 to lower surface 2 b of insulating substrate 2. Morespecifically, positive electrode lead-out structure 3 has positiveelectrode connection layer 31, positive electrode terminal 32, positiveelectrode plated layer 33, pillow member 34, and positive electrodebonding member 35. Positive electrode connection layer 31 is disposed onupper surface 2 a of insulating substrate 2, and has back surface 31 bthat is in contact with upper surface 2 a. Positive electrode terminal32 is disposed on lower surface 2 b of insulating substrate 2, and hasback surface 32 b that is in contact with lower surface 2 b. Inaddition, a metal foil sheet or metal plate composed of a metal materialis user for each of positive electrode connection layer 31 and positiveelectrode terminal 32. Furthermore, a plated layer may be formed on mainsurface 32 a of positive electrode terminal 32.

Positive electrode connection layer 31 has plural through holes ofpositive electrode connection layer 211 penetrating from main surface 31a to back surface 31 b. In addition, insulating substrate 2 has pluralthrough holes of insulating substrate 221 penetrating from upper surface2 a to lower surface 2 b. Thus, through hole of insulating substrate 221reaches back surface 32 b of positive electrode terminal 32. Here, eachthrough hole of positive electrode connection layer 211 is formed aboveeach through hole of insulating substrate 221. Therefore, through holeof positive electrode connection layer 211 and through hole ofinsulating substrate 221 are connected to each other. In addition,according to this exemplary embodiment, diameters of through hole ofpositive electrode connection layer 211 and through hole of insulatingsubstrate 221 are each preferably 50 μm to 150 μm.

Positive electrode plated layer 33 is formed on main surface 31 a ofpositive electrode connection layer 31, an inner surface of through holeof positive electrode connection layer 211, an inner surface of throughhole of insulating substrate 221, and back surface 32 b of positiveelectrode terminal 32 that is in contact with through hole of insulatingsubstrate 221. Thus, first positive electrode connection member 301 ofpositive electrode lead-out structure 3 comprises positive electrodeconnection layer 31, and a portion 331 in positive electrode platedlayer 33 that is formed on main surface 31 a of positive electrodeconnection layer 31 and on the inner surface of through hole of positiveelectrode connection layer 211. In addition, a positive electrodeconductive via comprises a portion in positive electrode plated layer 33formed on the inner surface of through hole of insulating substrate 221and back surface 32 b of positive electrode terminal 32, and thispositive electrode conductive via serves as second positive electrodeconnection member 302 of positive electrode lead-out structure 3. Thus,second positive electrode connection member 302 electrically connectsfirst positive electrode connection member 301 to positive electrodeterminal 32. In this way, first positive electrode connection member 301has plural first through holes 21 penetrating from its main surface (amain surface of positive electrode plated layer 33) to its back surface(back surface 31 b of positive electrode connection layer 31). Inaddition, second positive electrode connection member 302 has firstrecessed portion 22, and an inner side of first recessed portion 22links to first through hole 21 provided above. Furthermore, positiveelectrode plated layer 33 includes a material having high conductivitysuch as copper. In addition, according to this exemplary embodiment, athickness of positive electrode plated layer 33 is preferably 2 μm to 20μm, and positive electrode plated layer 33 is formed so as not tocompletely seal through hole of positive electrode connection layer 211and through hole of insulating substrate 221.

Pillow member 34 is interposed between lead-out portion 12 a of positiveelectrode lead 12 and first positive electrode connection member 301,and has top surface 34 a electrically connected to lead-out portion 12a, and bottom surface 34 b electrically connected to first positiveelectrode connection member 301. Consequently, pillow member 34electrically connects positive electrode lead 12 to first positiveelectrode connection member 301.

Here, a positional relation between pillow member 34 and first throughholes 21 is described with reference to FIGS. 1 and 2. FIG. 2 is a topview of region II illustrated in FIG. 1. In addition, exterior body 5 isnot illustrated in FIG. 2. As illustrated in FIGS. 1 and 2, pillowmember 34 has a rectangular parallelepiped shape, and bottom surface 34b of pillow member 34 has a rectangular shape having four corners 341and four sides 342. Furthermore, first positive electrode connectionmember 301 has six first through holes 21, in which four first throughholes 21 are formed to overlap with four corners 341, and two firstthrough holes 21 are formed to overlap with two sides 342. Furthermore,two sides 342 among four sides 342 extend parallel to each other in adirection roughly perpendicular to the extending direction of positiveelectrode lead 12.

According to the present disclosure, the positional relation betweenpillow member 34 and first through holes 21 is not limited to the aboverelation. For example, one or more first through holes 21 may be formedto overlap with at least one of four corners 341 and four sides 342.That is, the present disclosure includes a relation in which only onefirst through hole 21 overlaps with corner 341 or side 342, and arelation in which two or more first through holes 21 overlap with oneside 342. However, in order to make the position of pillow member 34coincide with predetermined position P with high precision in a sixthprocess in an electrode forming step that are described below, it ispreferable that at least two corners 341 among four corner 341 overlapswith first through holes 21 whose number corresponds to the number ofcorners 341, or at least two sides 342 among four sides 342 overlap withfirst through holes 21 whose number corresponds to the number of sides342.

Furthermore, the shape of bottom surface 34 b of pillow member 34 is notlimited to the rectangular shape, and it may be any kind of polygonalshape having a plurality of corners and a plurality of sides.Furthermore, the shape of bottom surface 34 b of pillow member 34 mayhave a curved portion such as a rounded polygonal shape, circular shape,or oval shape. In this case, one or more first through holes 21 arepreferably formed to overlap with the curved portion.

Positive electrode bonding member 35 bonds pillow member 34 to firstpositive electrode connection member 301. More specifically, positiveelectrode bonding member 35 partially enters first through holes 21, andis in contact with corners 341 or sides 342 of bottom surface 34 b ofpillow member 34, above first through holes 21. In addition, accordingto this exemplary embodiment, positive electrode bonding member 35 alsopartially enters first recessed portions 22 through first through holes21.

Positive electrode bonding member 35 includes a conductive materialcontaining a solder as a main component. More specifically, positiveelectrode bonding member 35 includes a conductive material havingwettability in a melted state with respect to first positive electrodeconnection member 301. According to this exemplary embodiment, a mainsurface of first positive electrode connection member 301 is provided aspositive electrode plated layer 33. Therefore, the solder is theconductive material having high wettability in a melted state withrespect to positive electrode plated layer 33 (a main surface of firstpositive electrode connection member 301).

Negative electrode lead-out structure 4 is an electrode structure thatleads a negative electrode current path connecting negative electrodelayer 15 to lower surface 2 b of insulating substrate 2. Morespecifically, positive electrode lead-out structure 4 has negativeelectrode connection layer 41, negative electrode terminal 42, andnegative electrode plated layer 43. Negative electrode connection layer41 is disposed on upper surface 2 a of insulating substrate 2 separatelyfrom positive electrode connection layer 31, and has back surface 41 bthat is in contact with upper surface 2 a. Negative electrode terminal42 is disposed on lower surface 2 b of insulating substrate 2 separatelyfrom positive electrode terminal 32, and has back surface 42 b that isin contact with lower surface 2 b. In addition, a metal foil sheet ormetal plate composed of a metal material is used for each of negativeelectrode connection layer 41 and negative electrode terminal 42.Furthermore, a plated layer may be formed on main surface 42 a ofnegative electrode terminal 42.

Negative electrode connection layer 41 has plural through holes ofnegative electrode connection layer 231 penetrating from main surface 41a to back surface 41 b. In addition, insulating substrate 2 has pluralthrough holes of insulating substrate 241 penetrating from upper surface2 a to lower surface 2 b. Thus, through hole of insulating substrate 241reaches back surface 42 b of negative electrode terminal 42. Here, eachthrough hole of negative electrode connection layer 231 is formed aboveeach through hole of insulating substrate 241. Therefore, through holeof negative electrode connection layer 231 and through hole ofinsulating substrate 241 are connected to each other. In addition,according to this exemplary embodiment, diameters of through hole ofnegative electrode connection layer 231 and through hole of insulatingsubstrate 241 are each preferably 50 μm to 150 μm.

Negative electrode plated layer 43 is formed on main surface 41 a ofnegative electrode connection layer 41, an inner surface of through holeof negative electrode connection layer 231, an inner surface of throughhole of insulating substrate connection layer 241, and back surface 42 bof negative electrode terminal 42 that is in contact with through holeof insulating substrate 241. Thus, first negative electrode connectionmember 401 of negative electrode lead-out structure 4 comprises negativeelectrode connection layer 41, and a portion 431 in negative electrodeplated layer 43 formed on main surface 41 a of negative electrodeconnection layer 41 and the inner surface of through hole of negativeelectrode connection layer 231. In addition, a negative electrodeconductive via comprises a portion in negative electrode plated layer 43formed on the inner surface of through hole of insulating substrate 241and back surface 42 b of negative electrode terminal 42, and thisnegative electrode conductive via serves as second negative electrodeconnection member 402 of negative electrode lead-out structure 4. Thus,second negative electrode connection member 402 electrically connectsfirst negative electrode connection member 401 to negative electrodeterminal 42. In this way, first negative electrode connection member 401has plural second through holes 23 penetrating from its main surface (amain surface of negative electrode plated layer 43) to its back surface(back surface 41 b of negative electrode connection layer 41). Inaddition, second negative electrode connection member 402 has secondrecessed portions 24, and an inner side of second recessed portion 24links to second through hole 23 provided above.

Furthermore, negative electrode plated layer 43 includes a materialhaving high conductivity such as copper. In addition, according to theexemplary embodiment, a thickness of negative electrode plated layer 43is preferably 2 μm to 20 μm, and negative electrode plated layer 43 isformed so as not to completely seal through hole of negative electrodeconnection layer 231 and through hole of insulating substrate 241.

Capacitor element 1 is connected to positive electrode lead-outstructure 3 and negative electrode lead-out structure 4 as follows. Thatis, lead-out portion 12 a of positive electrode lead 12 is welded to topsurface 34 a of pillow member 34, so that positive electrode lead 12 andpillow member 34 are electrically connected to each other. In addition,negative electrode layer 15 and first negative electrode connectionmember 401 are electrically connected to each other through conductivepaste 6 interposed between them.

Exterior body 5 covers capacitor element 1 on upper surface 2 a ofinsulating substrate 2. Meanwhile, exterior body 5 is not formed onlower surface 2 b of insulating substrate 2. Thus, main surface 32 a ofpositive electrode terminal 32 and main surface 42 a of negativeelectrode terminal 42 constitute lower surface electrodes of the solidelectrolytic capacitor. Furthermore, exterior body 5 includes anelectrical insulating material functioning as a sealing material such asan epoxy resin or silicone resin.

According to the solid electrolytic capacitor, while an edge (corners341 or sides 342) of bottom surface 34 b of pillow member 34 overlapswith first through holes 21, bottom surface 34 b mostly overlaps withthe main surface of first positive electrode connection member 301 (theflat main surface of positive electrode plated layer 33) except for aformation region of the first through hole 21. Therefore, pillow member34 is fixed on first positive electrode connection member 301 withpositive electrode bonding member 35 interposed between them. As aresult, pillow member 34 hardly inclines.

Next, a detailed description is given to a method for manufacturing thesolid electrolytic capacitor according to the first exemplaryembodiment. According to this exemplary embodiment, an electrode formingstep, an element disposing step, and an exterior body forming step areexecuted in this order. In the electrode forming step, positiveelectrode lead-out structure 3 and negative electrode lead-out structure4 are formed, and first to sixth processes are performed.

FIG. 3 is a cross-sectional view to be used for describing the firstprocess in the electrode forming step. As illustrated in FIG. 3, in thefirst process, metal foil sheets 51 and 52 including a metal materialsuch as copper are attached to upper surface 2 a and lower surface 2 bof insulating substrate 2, respectively. In addition, instead of metalfoil sheets 51 and 52, metal plates may be attached to upper surface 2 aand lower surface 2 b of insulating substrate 2.

FIGS. 4A and 4B are a cross-sectional view and a top view to be used fordescribing the second process in the electrode forming step,respectively. As illustrated in FIGS. 4A and 4B, in the second process,an etching process is executed on metal foil sheet 51 and insulatingsubstrate 2, whereby positive electrode connection layer 31 and negativeelectrode connection layer 41 are formed from metal foil sheet 51, andthrough hole of positive electrode connection layer 211, through hole ofinsulating substrate 221, through hole of negative electrode connectionlayer 231, and through hole of insulating substrate 241 are formed. Inaddition, an etching process is executed on metal foil sheet 52, wherebypositive electrode terminal 32 and negative electrode terminal 42 areformed from metal foil sheet 52.

According to this exemplary embodiment, as illustrated in FIG. 4B (referto also FIG. 2), six through holes of positive electrode connectionlayer 211 are formed in positive electrode connection layer 31. At thistime, six through holes of positive electrode connection layer 211 areformed so that the edge of bottom surface 34 b of pillow member 34overlaps with centers of all through holes of positive electrodeconnection layer 211 when pillow member 34 is disposed in predeterminedposition P. More specifically, six through holes of positive electrodeconnection layer 211 are formed so that four corners 341 of bottomsurface 34 b overlap with the centers of four through holes of positiveelectrode connection layer 211, and two sides 342 of bottom surface 34 boverlap with the centers of two through holes of positive electrodeconnection layer 211, respectively.

FIG. 5 is a cross-sectional view to be used for describing the thirdprocess in the electrode forming step. As illustrated in FIG. 5, in thethird step, a plating process is executed on main surface 31 a ofpositive electrode connection layer 31, the inner surface of throughhole of positive electrode connection layer 211, the inner surface ofthrough hole of insulating substrate 221, and an exposed region in backsurface 32 b of positive electrode terminal 32 due to the formation ofthrough hole of insulating substrate 221, whereby positive electrodeplated layer 33 is formed. In this way, first positive electrodeconnection member 301 and second positive electrode connection member302 are formed, first through holes 21 are formed in first positiveelectrode connection member 301, and first recessed portion 22 is formedin second positive electrode connection member 302. Furthermore, in thethird process, a plating process is executed on main surface 41 a ofnegative electrode connection layer 41, the inner surface of throughhole of negative electrode connection layer 231, the inner surface ofthrough hole of insulating substrate 241, and an exposed region in backsurface 42 b of negative electrode terminal 42 due to the formation ofthrough hole of insulating substrate 241, whereby negative electrodeplated layer 43 is formed. In this way, first negative electrodeconnection member 401 and second negative electrode connection member402 are formed, second through holes 23 are formed in first negativeelectrode connection member 401, and second recessed portion 24 isformed in second negative electrode connection member 402. In addition,in the third process, plated layers may be formed on main surface 32 aof positive electrode terminal 32 and main surface 42 a of negativeelectrode terminal 42. FIGS. 6A and 6B are a cross-sectional view and atop view to be used for describing the fourth process in the electrodeforming step, respectively. As illustrated in FIGS. 6A and 6B, in thefourth process, bonding agent 53 containing the conductive material isapplied to region R including the entire formation region of firstthrough holes 21 in the main surface of first positive electrodeconnection member 301 (the main surface of positive electrode platedlayer 33). According to this exemplary embodiment, solder pastecontaining solder powder and a flux is used as bonding agent 53.

FIGS. 7A and 7B are a cross-sectional view and a top view to be used fordescribing the fifth process in the electrode forming step,respectively. As illustrated in FIGS. 7A and 7B, in the fifth process,pillow member 34 is disposed on first positive electrode connectionmember 301, and bottom surface 34 b of pillow member 34 comes in contactwith bonding agent 53. At this time, four corners 341 of bottom surface34 b of pillow member 34 overlap with four first through holes 21described in an upper part and a lower part of FIG. 7B among six firstthrough holes 21. Furthermore, two sides 342 of bottom surface 34 b ofpillow member 34 overlap with two first through holes 21 described in amiddle part of FIG. 7B. Thus, pillow member 34 is disposed inpredetermined position P. However, in the fifth process, as illustratedin FIG. 8, the position of pillow member 34 could be displaced frompredetermined position P. Here, according to this exemplary embodiment,as illustrated in FIG. 7B, first through holes 21 are disposed so thatan area of a region surrounded by a line formed by connecting thecenters of four first through holes 21 overlapping with corners 341 ofpillow member 34 becomes equal to an area of bottom surface 34 b ofpillow member 34. Thus, this region makes predetermined position P.

FIGS. 9A and 9B are a cross-sectional view and a top view to be used fordescribing the sixth process in the electrode forming step,respectively. In the sixth process, the solder powder and the flux inbonding agent 53 are melted by heating bonding agent 53. The meltedsolder aggregates, and gets wet and spreads along bottom surface 34 b ofpillow member 34 and the main surface of positive electrode plated layer33. Here, the melted solder has high wettability especially with respectto positive electrode plated layer 33. Therefore, as illustrated bysolid arrows in FIG. 9A, the melted solder gets wet and spreads alongthe main surface of positive electrode plated layer 33, and flows intofirst through holes 21 and an inside of first recessed portion 22corresponding to first through holes 21. Consequently, the melted solderflows in bonding agent 53. Thus, due to this flow, pillow member 34receives forces in various directions along the main surface of positiveelectrode plated layer 33 (the main surface of first positive electrodeconnection member 301). When the position of pillow member 34 roughlycoincides with predetermined position P, as illustrated by outlinedarrows in FIGS. 9A and 9B, the forces applied to pillow member 34 canceleach other out, and as a result, pillow member 34 is maintained inpredetermined position P.

Meanwhile, when the position of pillow member 34 is displaced frompredetermined position P, a force applied in a direction displaced frompredetermined position P is smaller than a force applied in its oppositedirection as illustrated by outlined arrows in FIG. 10. As a result,pillow member 34 is drawn to predetermined position P, and the positionof pillow member 34 roughly coincides with predetermined position P.That is, the position of pillow member 34 is prevented from beinglargely displaced from predetermined position P.

After that, the solder and the flux are solidified. Thus, positiveelectrode bonding member 35 is formed, and a preferable state ofelectrical connection can be formed between pillow member 34 and firstpositive electrode connection member 301. In addition, the position ofpillow member 34 is fixed to predetermined position P or a positionslightly displaced from predetermined position P. Furthermore, positiveelectrode bonding member 35 partially enters each of first through holes21 and connected first recessed portions 22, so that an anchor effect isobtained, and as a result, bonding strength is improved between pillowmember 34 and first positive electrode connection member 301.

The element disposing step is described with reference to FIG. 1. In theelement disposing step, first, conductive paste 6 is applied to a mainsurface of first negative electrode connection member 401 (the mainsurface of negative electrode plated layer 43). Then, capacitor element1 is disposed on upper surface 2 a of insulating substrate 2. At thistime, a posture of capacitor element 1 is adjusted so that the extendingdirection of positive electrode lead 12 becomes parallel to uppersurface 2 a. In this way, lead-out portion 12 a of positive electrodelead 12 comes in contact with top surface 34 a of pillow member 34, andnegative electrode layer 15 comes in contact with conductive paste 6 onfirst negative electrode connection member 401. After that, a contactportion between positive electrode lead 12 and pillow member 34 iswelded.

As described above, according to the manufacturing method in the firstexemplary embodiment, the position of pillow member 34 is fixed topredetermined position P or the position slightly displaced frompredetermined position P. Therefore, when capacitor element 1 isdisposed on upper surface 2 a of insulating substrate 2, positiveelectrode lead 12 can be surely in contact with pillow member 34.Therefore, a preferable connection state can be formed between positiveelectrode lead 12 and pillow member 34 after the welding process, and asa result, an electrical connection defect is hardly generated.

The step of forming the exterior body is described with reference toFIG. 1. In the step of forming the exterior body, exterior body 5 ismolded on upper surface 2 a of insulating substrate 2 with a resin suchas an epoxy resin. More specifically, exterior body 5 is composed of asealing material containing the epoxy resin (base compound), an imidazolcompound (curing agent), and silica particles as a filler, and formed bytransfer molding. Thus, capacitor element 1 is covered with exteriorbody 5. In this way, the solid electrolytic capacitor is completed. Inaddition, instead of the epoxy resin, a silicone resin may be used asthe base compound of the sealing material.

Second Exemplary Embodiment

FIG. 11 is a cross-sectional view illustrating a solid electrolyticcapacitor according to a second exemplary embodiment of the presentdisclosure. Hereinafter, a description is given to positive electrodelead-out structure 3 and negative electrode lead-out structure 4, whichare different from the configurations of the first exemplary embodiment,among configurations in this solid electrolytic capacitor. Since theother configurations are the same as those of the first exemplaryembodiment, their descriptions are omitted.

According to the second exemplary embodiment, as illustrated in FIG. 11,positive electrode lead-out structure 3 has first positive electrodeconnection member 303 and second positive electrode connection member304 which are different in configuration from first positive electrodeconnection member 301 and second positive electrode connection member302 in the first exemplary embodiment. More specifically, secondpositive electrode connection member 304 is a positive electrodeconductive via composed of conductive material 36 filling through holeof insulating substrate 221. Thus, a main surface of conductive material36 recesses with respect to upper surface 2 a of insulating substrate 2.

First positive electrode connection member 303 is a metal layer formedon upper surface 2 a of insulating substrate 2 and the main surface ofthe conductive material 36. According to this exemplary embodiment, thismetal layer is a conductive plated layer and has a recess on the mainsurface of conductive material 36. That is, first positive electrodeconnection member 303 has plurality of recessed portions 25 formed bylocally recessing its main surface in positions on second positiveelectrode connection member 304 (positive electrode conductive via). Inthis way, according to the second exemplary embodiment, recessedportions 25 are formed instead of first through holes 21 in the firstexemplary embodiment. Thus, the positional relation between pillowmember 34 and first through holes 21 described in the first exemplaryembodiment is directly applied to a positional relation between pillowmember 34 and recessed portions 25 (refer to FIG. 2).

Positive electrode bonding member 35 partially enters recessed portions25 and is in contact with corners 341 or sides 342 of bottom surface 34b of pillow member 34 in positions above recessed portions 25 (refer toFIG. 2).

In addition, first positive electrode connection member 303 may be ametal foil sheet or metal plate composed of a metal material such ascopper. In this case, recessed portions 25 are formed by pressing themetal foil sheet or metal plate.

According to the second exemplary embodiment, as illustrated in FIG. 11,negative electrode lead-out structure 4 has first negative electrodeconnection member 403 and second negative electrode connection member404 which are different in configuration from first negative electrodeconnection member 401 and second negative electrode connection member402 in the first exemplary embodiment. More specifically, the secondnegative electrode connection member 404 is a negative electrodeconductive via composed of conductive material 37 filling through holeof insulating substrate 241. First negative electrode connection member403 is a plated layer formed on upper surface 2 a of insulatingsubstrate 2 and a main surface of conductive material 37.

FIG. 12 is a cross-sectional view illustrating another example ofpositive electrode lead-out structure 3. As illustrated in FIG. 12, themain surface of conductive material 36 serving as second positiveelectrode connection member 304 may go downward from upper surface 2 aof insulating substrate 2. According to this configuration, a depth ofrecessed portion 25 is increased.

Next, a method for manufacturing the solid electrolytic capacitoraccording to the second exemplary embodiment is described in detail.Hereinafter, a description is given to an electrode forming step, whichis different in configuration from that of the first exemplaryembodiment, among configurations in this manufacturing method. Inaddition, since other configurations are the same as those of the firstexemplary embodiment, their descriptions are omitted.

According to the second exemplary embodiment, the electrode forming stepis composed of first to seventh processes.

FIG. 13 is a cross-sectional view to be used for describing the firstprocess in the electrode forming step. As illustrated in FIG. 13, in thefirst process, metal foil sheet 52 composed of a metal material such ascopper is attached to lower surface 2 b of insulating substrate 2. Inaddition, instead of metal foil sheet 52, a metal plate may be attachedto lower surface 2 b of insulating substrate 2.

FIG. 14 is a cross-sectional view to be used for describing the secondprocess in the electrode forming step. As illustrated in FIG. 14, in thesecond process, an etching process is executed on insulating substrate2, whereby through holes of insulating substrate 221 and through holesof insulating substrate 241 are formed. At this time, through holes ofinsulating substrate 221 are formed so that the edge of bottom surface34 b overlaps with centers of all through holes of insulating substrate221 when pillow member 34 is disposed on predetermined position P (referto FIG. 4B). In addition, an etching process is executed on metal foilsheet 52, whereby positive electrode terminal 32 and negative electrodeterminal 42 are formed from metal foil sheet 52.

FIG. 15 is a cross-sectional view to be used for describing the thirdprocess in the electrode forming step. As illustrated in FIG. 15, in thethird process, through hole of insulating substrate 221 is filled withconductive material 36. At this time, by adjusting a filling amount ofconductive material 36, the main surface of the filled conductivematerial 36 recesses with respect to upper surface 2 a of insulatingsubstrate 2, or goes downward from upper surface 2 a. In addition,through hole of insulating substrate 241 is filled with conductivematerial 37. In this way, second positive electrode connection member304 and second negative electrode connection member 404 are formed.

FIG. 16 is a cross-sectional view to be used for describing the fourthprocess in the electrode forming step. As illustrated in FIG. 16, in thefourth process, a plating process is performed on upper surface 2 a ofinsulating substrate 2 and the main surface of conductive material 36,whereby a plated layer is formed as first positive electrode connectionmember 303. At this time, a thickness of the plated layer is adjusted sothat the main surface of the plated layer recesses on the main surfaceof conductive material 36. In this way, plurality of recessed portions25 are formed in first positive electrode connection member 303.Furthermore, a plating process is executed on upper surface 2 a ofinsulating substrate 2 and the main surface of the conductive material37, whereby a plated layer is formed as first negative electrodeconnection member 403. In addition, first positive electrode connectionmember 303 may be formed such that a metal foil sheet is attached toupper surface 2 a of insulating substrate 2 and the main surface of theconductive material 36, and then a plating process is executed on a mainsurface of the metal foil sheet. At this time, the metal foil sheet isformed along the recess of conductive material 36, whereby recessedportions 25 are formed in first positive electrode connection member303. First negative electrode connection member 403 may be similarlyformed.

FIG. 17 is a cross-sectional view to be used for describing the fifthprocess in the electrode forming step. As illustrated in FIG. 17, in thefifth process, bonding agent 53 containing the conductive material isapplied to region R including the entire formation region of recessedportions 25 in the main surface of first positive electrode connectionmember 303. According to this exemplary embodiment, solder pastecontaining solder powder and a flux is used as bonding agent 53.

FIGS. 18A and 18B are a cross-sectional view and a top view to be usedfor describing the sixth process in the electrode forming step,respectively. As illustrated in FIGS. 18A and 18B, in the sixth process,pillow member 34 is disposed on first positive electrode connectionmember 303, and bottom surface 34 b of pillow member 34 comes in contactwith bonding agent 53. At this time, four corners 341 of bottom surface34 b of pillow member 34 overlap with four recessed portions 25described in an upper part and a lower part of FIG. 18B among sixrecessed portions 25. Furthermore, two sides 342 of bottom surface 34 bof pillow member 34 overlap with two recessed portions 25 described in amiddle part of FIG. 18B. Thus, pillow member 34 is disposed inpredetermined position P. In addition, according to this exemplaryembodiment, as illustrated in FIG. 18B, recessed portions 25 aredisposed so that an area of a region surrounded by a line formed byconnecting centers of four recessed portions 25 overlapping with corners341 of pillow member 34 becomes equal to the area of bottom surface 34 bof pillow member 34. Thus, this region makes predetermined position P.

Subsequently, in the seventh process, the solder powder and the flux inbonding agent 53 are melted by heating bonding agent 53. In the seventhprocess, similar to the sixth process in the electrode forming step inthe first exemplary embodiment, the melted solder gets wet and spreadsalong bottom surface 34 b of pillow member 34 and the main surface ofpositive electrode plated layer 303, and flows into insides of recessedportions 25 (refer to FIG. 9B). Thus, the melted solder flows in bondingagent 53. As a result, pillow member 34 receives forces, and when theposition of pillow member 34 is displaced from predetermined position P,pillow member 34 is drawn to predetermined position P. That is, theposition of pillow member 34 is prevented from being largely displacedfrom predetermined position P.

After that, the solder and the flux are solidified. Thus, positiveelectrode bonding member 35 is formed, and a preferable state ofelectrical connection can be formed between pillow member 34 and firstpositive electrode connection member 303. In addition, the position ofpillow member 34 is fixed to predetermined position P or a positionslightly displaced from predetermined position P.

Therefore, according to the manufacturing method in the second exemplaryembodiment, similar to the first exemplary embodiment, when capacitorelement 1 is disposed on upper surface 2 a of insulating substrate 2,positive electrode lead 12 can surely come in contact with pillow member34. Thus, a preferable connection state is formed between positiveelectrode lead 12 and pillow member 34 after the welding process, and asa result, an electrical connection defect is hardly generated.

In addition, the configuration of each component in the presentdisclosure is not limited to the above exemplary embodiments, and thepresent disclosure can be modified in various ways within the technicalscope described in claims. For example, as illustrated in FIG. 19, inthe solid electrolytic capacitor according to the first exemplaryembodiment, positive electrode terminal 32 may have through hole 26linked to first through hole 21 by through hole of insulating substrate221.

According to the first exemplary embodiment, first through hole 21 isformed above the positive electrode conductive via serving as secondpositive electrode connection member 302. According to the secondexemplary embodiment, recessed portion 25 is formed above the positiveelectrode conductive via serving as second positive electrode connectionmember 304. However, the present disclosure is not limited to theseconfigurations. For example, as illustrated in FIG. 20, first positiveelectrode connection member 303 may have recessed portions 25 or throughholes in positions different from the position above the positiveelectrode conductive via. According to an example illustrated in FIG.20, recesses are formed in positions different from the formationposition of the positive electrode conductive via (second positiveelectrode connection member 304), in upper surface 2 a of insulatingsubstrate 2. Then, first positive electrode connection member 303 isformed along the recesses, whereby recessed portions 25 are formed. Inaddition, recessed portions 25 may be formed such that after firstpositive electrode connection member 303 has been formed, a pressingprocess is executed for first positive electrode connection member 303.

According to the above exemplary embodiments, bonding agent 53 used forforming positive electrode bonding member 35 is the solder pastecontaining the solder powder and the flux. However, the presentdisclosure is not limited to this configuration. Bonding agent 53 maycontain various kinds of conductive materials other than the solder.However, the conductive material preferably has wettability with respectto first positive electrode connection member in a melted state, so thatthe solder is especially preferable.

What is claimed is:
 1. A solid electrolytic capacitor comprising: aninsulating substrate having an upper surface and a lower surface; acapacitor element having a positive electrode member, a negativeelectrode member, and a dielectric member, and disposed on the uppersurface of the insulating substrate; a positive electrode lead-outstructure having a positive electrode terminal formed on the lowersurface of the insulating substrate, and electrically connected to thepositive electrode member of the capacitor element; and a negativeelectrode lead-out structure having a negative electrode terminal formedon the lower surface of the insulating substrate, and electricallyconnected to the negative electrode member of the capacitor element,wherein the positive electrode lead-out structure further comprises: afirst positive electrode connection member having a main surface and aback surface, of which the back surface is in contact with the uppersurface of the insulating substrate, a second positive electrodeconnection member configured to electrically connect the first positiveelectrode connection member to the positive electrode terminal, and apillow member having a top surface and a bottom surface, and configuredto electrically connect the positive electrode member of the capacitorelement to the first positive electrode connection member, wherein thefirst positive electrode connection member has a recessed portion formedby locally recessing the main surface, or a through hole penetratingfrom the main surface to the back surface, and the recessed portion orthe through hole overlaps an edge of the bottom surface of the pillowmember.
 2. The solid electrolytic capacitor according to claim 1,wherein: the recessed portion or the through hole has a first end and asecond end, the first end is disposed outside the edge of the bottomsurface of the pillow member, and the second end is disposed inside theedge of the bottom surface of the pillow member.
 3. The solidelectrolytic capacitor according to claim 1, wherein a center portion ofthe recessed portion or the through hole overlaps the edge of the bottomsurface of the pillow member.
 4. The solid electrolytic capacitoraccording to claim 1, wherein: the positive electrode member includes apositive electrode lead, the first positive electrode connection memberhas a plurality of recessed portions including the recessed portion, ora plurality of through holes including the through hole, and in a planarview from upper side of the insulating substrate, the plurality ofrecessed portions or the plurality of through holes are arranged in linesymmetry about the positive electrode lead.
 5. The solid electrolyticcapacitor according to claim 1, wherein the bottom surface of the pillowmember has a rounded polygonal shape that at least one of corners ofpolygonal shape is rounded.
 6. The solid electrolytic capacitoraccording to claim 1, wherein, at the recessed portion, a part of themain surface of the first positive electrode connection member ispositioned below the upper surface of the insulating substrate.
 7. Thesolid electrolytic capacitor according to claim 1, wherein: the bottomsurface of the pillow member has a shape having a plurality of sides,the first positive electrode connection member has a plurality ofrecessed portions including the recessed portion, or a plurality ofthrough holes including the through hole, and at least two of theplurality of recessed portions or at least two of the plurality ofthrough holes overlap one of the plurality of sides.
 8. The solidelectrolytic capacitor according to claim 1, wherein: a position of theback surface of the first positive electrode connection member at acenter of the recessed portion is below a position of an upper surfaceof the second positive electrode connection member at a periphery of therecessed portion.